1. Field of Invention
The present invention relates to a golf club, particularly to a golf club having a weight secured to a head body.
2. Prior Art
For example, a head of a wood club called metal wood is hollow, made of metallic materials. To manufacture such wood club head, a majority portion of a club head is constructed by casting, using a method such as lost wax, or otherwise, it is constructed from a few shell members, each being formed by pressing, then these shell members are joined together by welding or the like. To lighten a head and enlarging the same through the lightening thereof, titanium or titanium alloy has been used as metal materials.
In order to set various properties of a golf club, it is important to distribute the weight to respective portions of a head. For example, to enlarge a sweet area where a hit ball travels well and comparatively straight, said sweet area being positioned on a face or a ball hitting face at a front of a head, it is appropriate to enlarge a distance between the face and the center of gravity of a whole head (i.e., a depth of the center of gravity) or to disperse the weight toward the periphery of the face. To enable a hit ball to be raised easily so as to elongate a travelling distance, you may lower the center of gravity of a whole head. Further, a hit ball has a tendency to slice or hook, depending upon whether the position of the center of gravity of the whole head is located relatively close to a toe or a heel. You may take advantage of such tendency so as to correct a player's slicing or hooking habit. Besides, setting the weight distribution relative to each portion of a club head has a delicate influence on a feeling in hitting, and so on.
However, it is difficult to drastically vary a thickness per each shell if the shells are constructed by casting or forging only, and thus there has been a limit to the setting of the weight distribution relative to each portion of a club head. Conventionally, as disclosed in Japanese Un-Examined Patent Publication No.63-154186 for example, a balance weight which is separate from shells that construct a head body, has been joined to the inside face of the shell by welding or the like. Welding has been widely employed for joining such balance weight to the shell, due to it resulting in easy work and high joining strength. In the case of employing welding, however, the material of the shell member basically needs to be the same as that of the balance weight. For example, if the material of the shell member is titanium or titanium alloy, the material of the balance weight also must be titanium or titanium alloy. In that case, as titanium or titanium alloy is a lightweight material, it is difficult to obtain a sufficient effect of weight distribution by using such balance weight of titanium or titanium alloy.
On the other hand, if screwing or caulking is employed as a joining means, there would be no restriction on material. However, in the case of screwing, there is a likelihood to impair an appearance, as screws are exposed to the external. In the case of caulking also, caulking are often unable to be carried out due to a narrow inside and particular shape of a club head.
Whereas, in Japanese Patent Registered Publication No. 2606628 is proposed that a balance weight (weight body) of copper alloy or the like is screwed to a receiving base (weight base) of titanium alloy, then said receiving base is joined to a shell member (head body member) of titanium alloy by welding. With this construction, there is no restriction on weight material, while the balance weight screwed to the receiving base beforehand can be joined to the shell member by welding. However, since a means for joining the balance weight to the receiving body is screwing, the employment of screws that are separate from the balance weight and the receiving base would result in the increased number of components and the increased costs. Even if the screws are formed integrally with the balance weight, yet there would be problems that processing is made more complicated.